trying to upgrade a quadrajet - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 03-25-2006, 10:46 PM
Registered User
 
Join Date: Nov 2005
Location: cushing okla
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
trying to upgrade a quadrajet

I have a 56 chev car 4-speed 350 flat top pistons comp 274 cam,headers,373 posi rear end.I have a quadrajet I am trying to make run above 5500.It just acts like it runs out of fuel otherwise runs good.I have a comp series carb that will run up to about 6000 so I know it is getting enough fuel to the carb.The reason I want to fix the quadrajet is it has a lot better drivability on the street.The carb no is 17057213. It has 72 primary jets and 39b metering rods,It has secondary metering rods of DG.It has rod hangar of H.I hope somebody can give me some ideas on this.I was thinking about putting 75 primary jets.and a high performance needle and seat.I am sorry this is so long so I thought maybe someone with quadrajet experience could help me thanks phil

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-07-2006, 09:54 AM
Registered User
 
Join Date: Nov 2005
Location: Duffield ,Va
Age: 67
Posts: 526
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by perogers56
I have a 56 chev car 4-speed 350 flat top pistons comp 274 cam,headers,373 posi rear end.I have a quadrajet I am trying to make run above 5500.It just acts like it runs out of fuel otherwise runs good.I have a comp series carb that will run up to about 6000 so I know it is getting enough fuel to the carb.The reason I want to fix the quadrajet is it has a lot better drivability on the street.The carb no is 17057213. It has 72 primary jets and 39b metering rods,It has secondary metering rods of DG.It has rod hangar of H.I hope somebody can give me some ideas on this.I was thinking about putting 75 primary jets.and a high performance needle and seat.I am sorry this is so long so I thought maybe someone with quadrajet experience could help me thanks phil

Comp 274?
Now the Comp 270 has a power range 1800-5800, but I think you need to stay about 4-500 rpm under max rpm on shifting to get max power.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-07-2006, 10:24 AM
johnsongrass1's Avatar
Race it, Don't rice it!
 
Last photo:
Join Date: Jul 2002
Location: Columbia, Mo
Age: 37
Posts: 4,080
Wiki Edits: 0

Thanks: 0
Thanked 10 Times in 10 Posts
Q jet's are notorious for having small bowls and running out of fuel. Try upping the pressure or increaseing the Volume with a bigger needle and seat. See if you can grind way anything that will increase the bowl volume.

I see this happen to dirt racers on q jet's. They just don't like big engines at 7000 for extended periods.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-07-2006, 01:25 PM
Hippie's Avatar
Analog man in a digital world.
 

Last journal entry: HEI comparison.
Last photo:
Join Date: May 2003
Posts: 2,255
Wiki Edits: 0

Thanks: 3
Thanked 5 Times in 5 Posts
Quote:
Originally Posted by johnsongrass1
Q jet's are notorious for having small bowls and running out of fuel. Try upping the pressure or increaseing the Volume with a bigger needle and seat.
Don't go crazy on the pressure, the needle and seat won't hold after about 9 Lbs. if IIRC but maintaining steady pressure is important on a Q-Jet. One trick to increase fuel volume is to add a screw in fuel filter housing from an early 70's Q-Jet. I think it was mostly found on Buick's and Cadillacs. These screw in where the fuel line fitting normally went and are about 2 inches long. Leave the filter out and run an in line filter, this creates a small reservoir just outside the main fuel well. If you don't have Doug Roe's book on Rochester carbs buy a copy NOW, you'll be glad you did.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-08-2006, 02:07 AM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: 1999-2001: Getting it on the road
Last photo:
Join Date: Dec 2005
Location: Pittsburgh, PA
Age: 40
Posts: 5,128
Wiki Edits: 16

Thanks: 0
Thanked 2 Times in 2 Posts
Wait. The carb is a 750. Its NOT running out of fuel. The pump (provided its operating properly) and bowls (provided the floats are set right) are more than capable of supporting a 350 to 5500. I have a Qjet on a 467 that I spin to 5800 every day and its more than enough.

The carb doesn't determine your RPM range. The cam, heads, and compression do. You can put a huge race carb on that engine and it won't rev any higher. Its totally pointless to rev this engine above the cam and head's power band, which in this case seem to end at 5800.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-08-2006, 06:29 AM
Hippie's Avatar
Analog man in a digital world.
 

Last journal entry: HEI comparison.
Last photo:
Join Date: May 2003
Posts: 2,255
Wiki Edits: 0

Thanks: 3
Thanked 5 Times in 5 Posts
Quote:
Originally Posted by curtis73
Wait. The carb is a 750. Its NOT running out of fuel. The pump (provided its operating properly) and bowls (provided the floats are set right) are more than capable of supporting a 350 to 5500.
Good point Curtis, never overlook the obvious which we did. Have you checked the float level and read the plugs? It might be as simple as too low a float setting or you may need to make a jet, metering rod and/or hanger change.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 04-08-2006, 10:41 AM
Jmark's Avatar
Registered User
 
Last photo:
Join Date: Sep 2003
Location: phoenix
Age: 61
Posts: 4,808
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
I agree that the Q-jet should support sustained runs above 5 grand, but i've also noticed that some of the needle and seat sets in some kits leave much to be desired. The seat that has 2 slots cut in the side of it does flow more fuel into the bowl. The ones that are solid and only lets the gas flow up and around the needle seem to give problems in a high flow situation. Also, i personally like to get rid of the small filter that is behind the fuel inlet and instead run a good brand name 3/8" inline filter right before the carb.

You can also order a bigger needle and seat from www.carbs.net if you feel you still need more fuel. Just be careful because the bigger the needle area is, the more apt it is to give up under higher pump pressures. Qjets usually do just fine with an inlet pressure of 3-5 pounds with a clear filter.

Mark
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 04-09-2006, 03:12 AM
Member
 
Last photo:
Join Date: Aug 2005
Location: Yackandandah.Australia.
Age: 52
Posts: 641
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
You can also open up the float bowl into those two half inch holes at 11 and 1 o'clock(looking from above) to provide about 30% more area.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 04-09-2006, 04:09 AM
Twistedwrench's Avatar
No officer I won’t do it again
 
Last photo:
Join Date: Mar 2005
Location: Minnesota
Age: 45
Posts: 136
Wiki Edits: 0

Thanks: 1
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by Jmark
You can also order a bigger needle and seat from www.carbs.net if you feel you still need more fuel. Just be careful because the bigger the needle area is, the more apt it is to give up under higher pump pressures. Qjets usually do just fine with an inlet pressure of 3-5 pounds with a clear filter.

Mark
Just wanted to say thank you myself for that link. For two weeks I have been trying to find the gm part # 78035142 .136 needle and seat. I have had no luck. The original part number has been discontinued and changed over. I have tried the local dealership and all the parts stores around me with no luck. This was supposed to be the best one out there for the Qjet providing extra fuel flow into the bowl. Not only does that link have it but they have even a better one! You just made my day! And as to the original question on the board. I would go for this same needle and seat. Part # C1980 .147 inlet. ( but let me get mine first in case they run out!) lol
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 04-09-2006, 05:37 AM
Registered User
 
Last photo:
Join Date: Nov 2004
Location: Cali
Posts: 994
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by IanRiordan
You can also open up the float bowl into those two half inch holes at 11 and 1 o'clock(looking from above) to provide about 30% more area.
These would be the secondary accelerator circuit wells, removing the dividing wall will drastically alter the operation of the carb. It will allow the secondaries to suck way too much fuel out of the bowl through the accelerator tube.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 04-10-2006, 04:07 AM
Registered User
 
Join Date: Nov 2005
Location: cushing okla
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I think I have qjet fixed

I ordered high performance needle and seat from Summit.I put larger primary jets I went from 72 to 75.I ordered a new sec. metering rods and a b holder.I tryed it yesterday I think it is going to work. Thanks phil
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 04-10-2006, 11:20 AM
Jmark's Avatar
Registered User
 
Last photo:
Join Date: Sep 2003
Location: phoenix
Age: 61
Posts: 4,808
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Those changes will for sure richen it up! Just make sure your fuel pressure is in line, 3-5 pounds. If not, higher pressures will overpower the larger needle and seat and flood like crazy!

Mark
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 04-11-2006, 05:22 AM
Member
 
Last photo:
Join Date: Aug 2005
Location: Yackandandah.Australia.
Age: 52
Posts: 641
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I ran a 72 Q - jet so modified for years on a 350/muncie/3.00 9in equiped hq Holden ute (like a 70 el camino). It ran 12.68 in street trim, towed my 18 ft ski boat and got 18mpg on the highway (14/15 towing). I ran stock secondary rods and hanger, it never missbehaved or ran rich - wish I still had it.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 04-11-2006, 12:36 PM
Registered User
 
Join Date: Nov 2005
Location: cushing okla
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
quadrajet runs good on street

I looked for a long time a while back trying to find out what cfm a quadrajet was.Then one day someone talked about a web site that said qjet are 750 and I think 800 cfm.I know it runs alot better than my 750 carter afb on the street.They dont seem to cause a lot of drivability problems.I just had the one problem when I took it to the drags and when it hit about 5000 it acted like it was starving fuel.I later tryed the 750 carter afb and it would run all the way through the gears. So i knew it had to be the carb but I think I have it fixed now.It is hard find a place on the street to test it at 5000 onthe street in fourth gear.They might take you to jail. Thanks phil
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ignition upgrade..ur info appreciated 85GrandPrix350 Hotrodding Basics 3 03-11-2006 01:01 PM
60 Thunderbird Suspension Upgrade. 60tbirdrick Suspension - Brakes - Steering 7 08-14-2005 08:38 PM
Which Quadrajet for 67 Ram Air? 67firebird General Rodding Tech 8 12-11-2004 10:07 PM
1976 Quadrajet help needed janetdennyh Introduce Yourself 1 11-24-2004 08:10 AM
Brake / Suspension Upgrade - 75 Chevy Pickup dwstevenson Suspension - Brakes - Steering 0 12-31-2002 07:42 AM


All times are GMT -6. The time now is 05:55 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.